Determination of quality in stored pear fruits by chemical analysis and sensorial judgement

Pear (Pyrus communis L.) belongs to the family Rosaceae and subfamily Pomoideae. It is one of the most important tree fruit of the world. Out of the several species the pear is most widely grown. The pear is considered by many to be among the most delicious of all species. It contains a better juicy texture with a delicate fl avour and aroma (Iftikhar et al., 2009). The common Hungarian varieties of pear are Bosc kobak, Conference, Packham’s Triumph and Williams pear. Except the William pear the other pears are winter varieties and can be stored for longer period. Eating quality is diffi cult to measure objectively. Analytical measurements of soluble solids (% SS), titratable acidity (TA) and fi rmness have shown poor correlation with sensory perceptions of sweetness, sourness and texture (Bourne, 1979, Watada et al., 1981). Fruit quality includes many properties such as sensory attributes (appearance, texture and fl avour), nutritional value, chemical constituents, mechanical properties, functional properties and defects (Abbott, 1999). The quality attributes can be described by colour, texture fl avour, and taste (sweet, sour, salt and bitter sensations) in addition to physical attributes such as size and shape. All these attributes can be evaluated by using trained sensory panel, but more rapid and objective characterisation is achieved by instrumental measurements. Texture and fl avour appear to be the most important attributes for the consumer (Stow, 1995) Appearance of fruit in the marketplace is a critical importance to consumer, often setting up expectation of what the product will taste like (Deliza & MacFie, 1996; Jaeger & MacFie, 2011). External factors of the appearance of fruit, such as shape and colour, can have a large infl uence on the consumer’s fi rst impression and opinion of what the fruit may taste like (Jaeger & MacFie, 2001). Colour is probably the most important appearance characteristic of foods, especially if some other aspect of quality is related to the colour. It seems likely that recognition of cultivar as well as Determination of quality in stored pear fruits by chemical analysis and sensorial judgement


Introduction
Pear (Pyrus communis L.) belongs to the family Rosaceae and subfamily Pomoideae.It is one of the most important tree fruit of the world.Out of the several species the pear is most widely grown.The pear is considered by many to be among the most delicious of all species.It contains a better juicy texture with a delicate fl avour and aroma (Iftikhar et al., 2009).The common Hungarian varieties of pear are Bosc kobak, Conference, Packham's Triumph and Williams pear.Except the William pear the other pears are winter varieties and can be stored for longer period.
Eating quality is diffi cult to measure objectively.Analytical measurements of soluble solids (% SS), titratable acidity (TA) and fi rmness have shown poor correlation with sensory perceptions of sweetness, sourness and texture (Bourne, 1979, Watada et al., 1981).
Fruit quality includes many properties such as sensory attributes (appearance, texture and fl avour), nutritional value, chemical constituents, mechanical properties, functional properties and defects (Abbott, 1999).
The quality attributes can be described by colour, texture fl avour, and taste (sweet, sour, salt and bitter sensations) in addition to physical attributes such as size and shape.All these attributes can be evaluated by using trained sensory panel, but more rapid and objective characterisation is achieved by instrumental measurements.Texture and fl avour appear to be the most important attributes for the consumer (Stow, 1995) Appearance of fruit in the marketplace is a critical importance to consumer, often setting up expectation of what the product will taste like (Deliza & MacFie, 1996;Jaeger & MacFie, 2011).External factors of the appearance of fruit, such as shape and colour, can have a large infl uence on the consumer's fi rst impression and opinion of what the fruit may taste like (Jaeger & MacFie, 2001).Colour is probably the most important appearance characteristic of foods, especially if some other aspect of quality is related to the colour.It seems likely that recognition of cultivar as well as
Summary: Aim of this research/project to determine the external and internal preferences of pear using descriptive sensory analysis, consumer preference.The research was performed on local consumers.Destructive measurements included fi rmness by puncture tests, soluble solids content (SSC), titrated acidity (TA).While there is a general positive trend for increasing preference with fi rmness, some consumers will prefer softer apples, and some will dislike the fi rmest pear.
Sensorial judgement is able to classify the attractiveness, preference of properties specifi c for pear.Tests were performed by 13 persons on 4 pear varieties (Bosc kobak, Conference, Packham's Triumph, Dessertnaia) checking 11 sensorial properties on a scale of 1 to 100 points.Relations of measurements and judgements were processed by correlation analysis.For analysis, the objects were furnished in 2011 from different growing sites (Csenger, Mérk and Nagykanizsa), taking from the store (in January) immediately.Among those the best notes were given to Bosc kobak and Conference coming from Mérk and to Packham's Triumph grown at Nagykanizsa.It was stated that the success of sensorial judgement depends on the state of maturity, which is diffi cult to guarantee to be synchronous among samples of different varieties.Mature fruits are more praised as a sample of Bosc kobak taken from a chain of department store proved to be of balanced composition regarding its sugar/acid ratio (0.12) and the optimal fi rmness (5.75 N/cm 2 ).
Results of the correlation analysis suggest that the thickness of the skin is a decisive component of preference (r= 0.857), the typical pearfl avour (r= 0.948), the taste as sweetness and acidity (r= 0.930 and r= 0.813).At the same time, no valuable relation could be detected between the data raised in the laboratory and the preference expressed by the sensorial tests, which should signalise that the opinion of consumers does not depend on any individual parameter obtained in the laboratory (sugar-or acid content, fi rmness) but rather on the complexity of several decisive components together (sweetness, acidity, fl avour, skin, etc.).The consumers' preference cannot be measured objectively without the aid of adequate expertise and a prosperous surrounding, samples of optimal maturity and a thoughtfully edited judging form the general appearance and condition of produce is important to pear purchasers.Flavour is specifi cally important that fresh fruits have an excellent external appearance in addition to good fl avour and texture (Suwanagul & Richardson, 1998).The fl avour of a food product includes the olfactory sensations caused by volatile substances released from the product (aroma), gustatory sensations (taste) and trigeminal sensations such as astringency (Meilgaard et al., 1987).It is, however, well known that the colour and texture of food products can also infl uence the overall judgment of a particular fl avour (Redgwell & Fischer, 2002).Aroma is one of the most important sensory attributes of fruit (Zhang et al., 2008).It has been found that there are close correlations between pear aroma and fl avour which indicates the importance of volatile aromatics to fl avour as they make a pear taste like a pear (Eccher Zerbini, 2002;Quamme & Marriage, 1977).
Texture was defi ned by Szczesniak (1990) as "the sensory manifestation of the structure of the food and the manner in which this structure reacts to the applied forces, the specifi c senses being involved being vision, kinaesthesia, and hearing".It is an important quality attribute of fresh fruit and vegetables, however, fl avour often overshadows the texture of a product (Nicolai et al., 2003).Ripening is the key factor for fruit texture and thus ultimately fruit quality.
Sensory analysis plays a large role in supporting breeding and introduction of new cultivars into the marketplace (Hampson et al., 2000).Sensory analysis has been defi ned as "a scientifi c discipline used to evoke, measure, analyse, and interpret reactions to those characteristics of foods and materials as they are perceived by the senses of sight, smell, taste, touch, and hearing" (IFT, 1975).
For quality evaluation of pears sensory, chemical and physical measurements are often determined.Instrumental texture measurements, as well as sugar and acid contents are rapid measurements used to determine quality of apples after harvest and to follow changes during storage.
One of the challenges in sensory evaluation of fruit is product variability.Differences in soil, climate and cultural management produce site-to-site variation, while individual fruit off the same tree may vary in characteristics such as fi rmness, % SS, acidity and colour.This variation is not always evident externally and so cannot be controlled by visual classifi cation.In addition, perceptible differences in sweetness, crispness and fruit fl avour exist within fruits from top to bottom and side to side (Dever et al., 1995)

Material and method
Five fresh, mature and healthy commercially grown pear cultivar was harvested in Csenger, Merk and Nagykanizsa in August 2011.For the excellent maturity, taste, fl avour, smell, crispiness pears have been stored at +0,5 0C at GYKSZNK Kft. in Ujfeherto.The recommended interval of temperature in the store is +0,5 and -0,1 0C.Higher temperatures reduce the possible storing period substantially (Soltesz, 1997).Two of the 13 samples were purchased from Tesco and Cora hypermarkets in Debrecen.Before the sensory analysis started the internal preferences (total soluble solids, acid and fl esh fi rmness) of the pears have measured.After washing, sorting and coring the fruit pieces were made with the help of stainless steel knife and placed on a plate.On another plate the whole fruits were put.
For the performance of the session we applied the principles and methods earlier developed (Takácsné Hájos et al., 2010).Samples coming from different sites have been coded.On the form 11 questions have to be answered and each will be rated on a scale of 1-100.
Results are visualised by diagrams, and the relations revealed as correlations.

Results and discussion
Results of measurements and tests performed in the laboratory and the ratings of the sensorial sessions are presented in Table 1 and Figure 1.The maximum of points is 1100.Best rate received the variety Bosc kobak (933.58 points as mean of all tests), on the best growing site, Mérk (953.08),almost the same value at Nagykanizsai in ULO store (946.25).
The value of the samples depends largely on the maturity of fruits taken from the department stores.Those Bosc samples furnished by the store of Cora were optimally ripe, i.e. ready for consumption.The adequate sign of maturity is the fi rmness, which showed about half of the values of other samples (5.75 N/cm 2 ).On the contrary, water soluble solids were as high as the mean of varieties (14.18 %), whereas acidity (1.64 %) was two times higher.That sample gave the highest sugar/acid ratio (0.12), which was prosperous from the point view of sensorial rating and thus achieved the highest record (993.42).
Samples of Conference excelled also when coming from Mérk (total being 935 points), which means good sugar (14.75 %) and acids (1.08 %), which also being in optimal for taste.
Among samples coming from the same growing sites, Packham's Triumph proved to be the next best variety, but samples of Nagykanizsa received the highest number of points: 895.75.Firmness of samples was nearly equal in the three samples (8.20-8.66N/cm 2 ), but the water soluble solids was higher at Nagykanizsa (15.56 %) combined with a lower acid content (0.58 %).
As visible in the results, that not so much the absolute value of parameters alone were appreciated by the panel, but rather the relations or harmony between the properties (e.g.sugar/acid ratio), which could be expressed by the word: taste.Diagrams of Figure 1 show the points given to fruits of three pear varieties grown at different sites after sensorial rating.The best score was given to Bosc kobak coming from the chain store Cora, while the other two varieties proved to be slightly inferior: Conference and Packham's Triumph.
The ratings of the sensorial tests was depicted by radial diagrams (Figure 2-4), where all the 13 persons' expressed their opinion.The saturation of the shape means the uniformity of the properties observed.It's best recognised in Bosc kobak (Figure 2), where all values of the score were high in the diagram.Among the most mature samples, it was unique in earning near maximum score in fl avour.
Thus, it is convincing that full maturity is the most adequate period, when decisions are most valid, i.e. ready for immediate consumption.In the future, we must agree that the most important components of the quality do not attain their maxima at the same time.If fragrance and fl avour are considered, taste, sweetness and acidity cannot be optimal in spite if genetically well founded.The variety Conference was represented by three growing sites, where the commune Mérk proved to be the best, although the typical pear fl avour was not appreciated (Figure 3).
In Figure 4, three samples of Packham's Triumph were combined with the data of Dessertnaia, which was stored in the same ULO (ultra low oxygen) store at Nagykanizsa, and was appreciated for its special fl avour and smell.
The correlations between the scores of the sensorial tests and the data obtained in the laboratory are presented in the matrix of Table 2.
It could be stated that the popularity of fruits is largely determined by the thickness of the fruit peel (r=0.857),fl avour (r= 0.800), and by the aroma (r= 0.948), sweetness (r= 0.930) and freshness due to the acidity (r=0.813).
Those relationships prove the decisive components: fl avour, taste and aroma being considered fi rst of all.It is important that the samples must represent identical state of maturity.The relation between taste: acidity and sweetness (r= 0.749) tells us the important harmony being equally contributed by both components.Similarly, the fi rmness and fl avour are closely related with sweetness and special pear fl avour.
As no one parameter of measurements obtained in the laboratory showed close relation with sensorial scores.It tells us that the content of acids or sugar alone does not decide the value of the fruit from the point of view of the consumer.Those components together are responsible for the harmony of taste and for freshness.

Figure 1 .
Figure 1.Records of sensorial ratings of fruits coming from different sources of three varieties

Table 1 .
Comparison of the results of sensorial tests and measurements obtains in the laboratory regarding the quality of pear varieties.Debrecen, 2012 *points obtained for 11 properties (maximum: 1100 points)

Table 2 .
Matrix of correlations between sensorial scores and data obtained by laboratory tests on pear fruits (n=13) *parameters received from the onganoleptic panel